The need for noninvasive techniques to evaluate perfusion and metabolism of normal and abnormal myocardium is well recognized. Recently, nuclear medicine imaging techniques have provided useful information on coronary blood flow and myocardial metabolism using T1-201 T1C13, C-11 or I-123 fatty acids. In order to improve routine nuclear medicine heart imaging, it is necessary to develop better radiopharmaceuticals, especially Tc-99m labeled agents, which has optimal physical characteristics for gamma camera imaging. A good myocardial imaging agent should have high initial extraction (nearly 100% first pass extraction) reflecting regional myocardial perfusion, and subsequently the retention time may reflect metabolism. Such agents will certainly provide diagnostic information to evaluate myocardial functions. The overall objective of this project is to develop Tc-99m labeled fatty acid analogs for noninvasive myocardial imaging. Compounds containing neutral Tc-99m carrier, BAT(bis-aminoethanthiol), and long unbranched and beta-methyl branched fatty acid side chain will be prepared, labeled, and then evaluated in rats and monkeys by dissection and gamma camera imaging technique, respectively. The proposed Tc-99m fatty acid analogs are designed to have specific physical-chemical properties mimicking natural fatty acids. They will cross the myocardial cell membrane by passive diffusion and subsequently be metabolized by beta-oxidation. After an i.v. injection of these Tc-99m agents the regional myocardial perfusion and fatty acid metabolism can be evaluated by gamma camera imaging - a routine nuclear medicine procedure.